[PATCH v2] test/argparse: change initialization to workaround LTO

[Stephen Hemminger <stephen@networkplumber.org>]

When compiled with Link Time Optimization, the existing code
generated an error, because the compiler was unable to intuit
that there was space in the flexible array.

In function ‘test_argparse_copy’,
    inlined from ‘test_argparse_init_obj’ at ../app/test/test_argparse.c:108:2,
    inlined from ‘test_argparse_opt_callback_parse_int_of_no_val’ at ../app/test/test_argparse.c:490:8:
../app/test/test_argparse.c:96:17: warning: ‘memcpy’ writing 56 bytes into a region of size 0 overflows the destination [-Wstringop-overflow=]
   96 |                 memcpy(&dst->args[i], &src->args[i], sizeof(src->args[i]));

Initialiizing a structure with flexible array is special case
and compiler expands the structure to fit. But inside the copy
function it no longer knew that.

The workaround is to put the copy inside the same function
and use structure assignment. Also macro should be uppper case.

Fixes: 6c5c6571601c ("argparse: verify argument config")
Cc: fengchengwen@huawei.com

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
v2 - simpler fix is to just inline the copy

 app/test/test_argparse.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/app/test/test_argparse.c b/app/test/test_argparse.c
index 0a229752fa..d5b777e321 100644
--- a/app/test/test_argparse.c
+++ b/app/test/test_argparse.c
@@ -71,7 +71,7 @@ test_argparse_callback(uint32_t index, const char *value, void *opaque)
 }
 
 /* valid templater, must contain at least two args. */
-#define argparse_templater() { \
+#define ARGPARSE_TEMPLATE { \
 	.prog_name = "test_argparse", \
 	.usage = "-a xx -b yy", \
 	.descriptor = NULL, \
@@ -87,25 +87,24 @@ test_argparse_callback(uint32_t index, const char *value, void *opaque)
 	}, \
 }
 
-static void
-test_argparse_copy(struct rte_argparse *dst, struct rte_argparse *src)
-{
-	uint32_t i;
-	memcpy(dst, src, sizeof(*src));
-	for (i = 0; /* NULL */; i++) {
-		memcpy(&dst->args[i], &src->args[i], sizeof(src->args[i]));
-		if (src->args[i].name_long == NULL)
-			break;
-	}
-}
 
 static struct rte_argparse *
 test_argparse_init_obj(void)
 {
-	static struct rte_argparse backup = argparse_templater();
-	static struct rte_argparse obj = argparse_templater();
-	/* Because obj may be overwritten, do a deep copy. */
-	test_argparse_copy(&obj, &backup);
+	/* Note: initialization of structure with flexible arrary
+	 * increases the size of the variable to match.
+	 */
+	static const struct rte_argparse backup = ARGPARSE_TEMPLATE;
+	static struct rte_argparse obj = ARGPARSE_TEMPLATE;
+	unsigned int i;
+
+	obj = backup;
+	for (i = 0; ; i++) {
+		obj.args[i] = backup.args[i];
+		if (backup.args[i].name_long == NULL)
+			break;
+	}
+
 	return &obj;
 }
 
-- 
2.47.2